Manufacturers of disk drives perform what is commonly known as ongoing reliability testing in order to assess the quality of their disk drives as well as to monitor and improve their manufacturing process. As a part of ongoing reliability testing, customer usage simulations are performed on a sample of disk drives that represents, for example, manufactured disk drives for a period of time, such as a week. Customer usage simulations can represent the way that the disk drives will be used by customers who will potentially buy the disk drives. In conventional ongoing reliability testing, disk drives that have hard failures are analyzed to determine the core reason for their failures. The results of the analysis are used to improve the manufacturing process in order to prevent those types of failures occurring in future disk drives.
Further, the results of the analysis can also be used to determine whether to a certain batch of disk drives are good enough to be sold to customers. For example, if the number of disk drives that fail the ongoing reliability test exceeds an acceptable threshold, a risk assessment is performed. For example, the risk assessment may involve determining whether the customer usage simulations represent the customers that the disk drives the sample was taken from will be sold to. For example, disk drives are typically rated for 1 million hours mean time to failure. If a customer typically uses their disk drives less than 1 million hours, then the risk of selling disk drives to that customer is less.
Customers who buy disk drives typically require that ongoing reliability testing be performed. Certain results, such as throughput and seek time, from the ongoing reliability testing are typically provided to the customers. For the foregoing reasons, it can be seen that ongoing reliability testing is of great importance.